This should not be closed.
Tumblr works similar to Google+ Pages and/or Facebook pages. I can have my own Facebook, but be made admin of any number of other Pages.
I have my own personal tumblr, but I’ve also been made an admin for a company Tumblr.
I do have access to the site, but when you create the Tumblr “app” necessary to interact with the WordPress Plugin, it defaults you to the login’s main blog.
